The Development of Polymers
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The Development of Polymère In May 1922, Herrhann Staudinger, a chemist in Germany, published a paper proposing that rubber was actually a "macromolecule," a chain of isoprene units. Other chemists raised such vocal opposition to this idea that Staudinger plunged into other intensive studies, eventually showing through examination of the viscosities of its solutions that styrène resin (which he renamed polystyrène) is also an assembly of macromolecules, giant polymers of varying lengths. Staudinger's persistence laid the theoretical background for the entire polymer industry, which produces about 25 billion pounds of plastic each year in the Unités States alonè. A "plastic" is a polymer-based material hardened from the liquid state into one that has some degree of structural rigidity. While several polymers occur naturally— such as shellac, rosin, and gutta-percha— most mariufactured plastics begin with petroleum raw materials. Chemist Alexander Parkes created the first plastic, Parkesine (later called xylonite), in England in 1862. Parkes began with cellulose nitrate, which he obtained by treating cotton linters (the short fibers left over after ginning, which removes the long staple fibers) in a mixture of nitric acid and sulfuric acid. Wood pulp treated with alkali also provides another natural source of cellulose (itself a natural polymer made of glucose units). Parkes softened his nitrocellulose with vegetable oils and a small amount of camphor, which yielded a crude plastic material. Six years after Parkes' discovery, John W. Hyatt in the United States recognized the importance of adding camphor to cellulose nitrate. Mixing the cellulose nitrate with alcohol and camphor yields a plastic mass that can be rolled into sheets, pressed into a block, and then dried and polished to the required form. Hyatt molded theriewplastic material into billiard balls, combs, détachable collars, and other articles. Originally considered the best substitute for ivory and tortoiseshell, this material found substantial early uses in carriage and automobile windshields. The same plastic, called celluloid, was introduced as a photographie film base in 1884 by the Eastman-Kodak Company (see Historical Note in the June 1989 MRS Bulletin). Cellulose treated with acetic acid, called cellulose acétate, was a clear, tough material, also used over the next several
décades as a photographie film base. Cellulose triacetate, which is soluble in toxic solvents, was used as a waterproof varnish for the fabric on airplane wings. Transparent acétate film also became popular for packagingThe first completely synthetic polymer resin was patented in the United States in 1909 by Léo Hendrik Baekeland. He named his hardened amberlike material, produced from phénol and formaldehyde, "Bakélite." (See Historical Note in the July 1989 MRS Bulletin.)
High-density polyethylene made its first public appearance in the form of hula hoops. In 1835 the reaction of acétylène with hydrochloric acid was found to produce vinyl chloride, but not until 1912 was this
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